Abstract.Two classes of nominal automata, namely Usage Automata (UAs) and VariableFinite Automata (VFAs) are considered to express resource control policiesover program execution traces expressed by a nominal calculus (Usages).We first discuss some closure properties of UAs, and then show UAs lessexpressive than VFAs.We finally carry over to VFAs the symbolic technique for model checkingUsages against UAs, so making it possible to verify the compliance of aprogram with a larger class of security properties.